The present invention is based on the phenomenon of dielectrophoresis--the translational motion of neutral matter caused bu polarization effects in a non-uniform electric field. The dielectrophoresis phenomenon was first recorded over 2500 years ago when it was discovered that rubbed amber attracts bits of fluff and other matter. Over 300 years ago, it was observed that water droplet change shape as they approach a charged piece of amber. The basic concept of dielectrophoresis is examined in detail in a text entitled Dielectrophoresis by Herbert H. Pohl, published in 1978 by the Cambridge University Press. Further discussion of this phenomenon also can be found in an article by W. F. Pickard entitled "Electrical Force Effects in Dielectric Liquids," Progress in Dielectrics 6 (1965)--J. B. Birks and J. Hart, Editors.
All known practical applications of the dielectrophoresis phenomenon have been directed to either separators or clutches. For example, U.S. Pat. No. 1,533,711 discloses a dielectrophoretic device that removes water from oil; U.S. Pat. No. 2,086,666 discloses a dielectrophoretic device which removes wax from oil; U.S. Pat. No. 2,664,246 discloses a dielectrophoretic separator used in a sludge treatment process, U.S. Pat. No. 2,914,453 provides for separation of solid polymeric material from fluid solvents; U.S. Pat. No. 3,162,592 provides for separation of biological cells; U.S. Pat. No. 3,197,393 discloses a separator using centripetal acceleration and the dielectrophoretic phenomenon; U.S. Pat. No. 3,304,251 discloses dielectrophoretic separation of wax from oil; U.S. Pat. No. 3,431,441 provides a dielectrophoretic separator which removes polarizable molecules from plasma; U.S. Pat. No. 3,980,541 discloses separation of water from fluid; and U.S. Pat. No. 4,164,460 provides for removal of particles from a liquid. U.S. Pat. Nos. 3,687,834; 3,795,605; 3,966,575; and 4,057,482 disclose other dielectrophoretic separators for removing particulates and water from a fluid. Other separators, not necessarily dielectrophoretic separators, are disclosed in U.S. Pat. Nos. 465,822; 895,729; 3,247,091 and 4,001,102.
U.S. Pat. No. 2,417,850 discloses a clutch mechanism using the dielectrophoretic phenomenon.
The object of the present invention is to provide a method and apparatus for storing and retrieving information using the phenomenon of dielectrophoresis. A variety of electronic memory devices are well known in the art. The two general classes of such memory devices are electric field devices, such as static and dynamic random access memories, (RAM), and charge-coupled devices, (CCDs), while the second class is magnetic field devices, such as cores, disk, tape, and magnetic bubbles. In general, the very fast random access memories are expensive, due in part to the high cost of their substrate material. Large capacity memories are less expensive when constructed out of magnetic materials, however the time required to access the data usually increases with the data capacity. Magnetic systems such as disk and tape can have high data transfer rates, but they are subject to mechanical wear. Magnetic bubble memories have no moving mechanical parts, but also have slower data rates and more expensive substrate materials. The present invention provides a non-volatile random access memory of moderate speed, requiring a very low cost substrate material. The data capacity and speed of this device place it between the fast electric field devices and the large capacity magnetic field devices in performance. The design is insensitive to electromagnetic noise and cosmic ray effects, and can operate over a wide temperature range. Information is stored by the manipulation of materials by dielectrophoretic forces resultant from the application of non-uniform electric fields thereto.